1. Field of the Invention
The invention relates to a foldable supporting device, more particularly to a foldable supporting device including supporting frames aligned in a direction and foldable units interconnecting the supporting frames and foldable in the direction.
2. Description of the Related Art
Referring to FIG. 1, U.S. Pat. No. 6,581,223 discloses a conventional foldable frame assembly that includes a plurality of supporting frames 7 aligned in a folding direction, and a plurality of foldable units 8, each of which is disposed between and interconnects an adjacent pair of the supporting frames 7, each of which is foldable in the folding direction, and each of which includes a pair of crossing rods 81, a pair of first linking rods 82, a pair of second linking rods 83, a middle beam 84, a pair of upper joints 85 and a pair of lower joints 86. Each of the supporting frames 7 has a pair of pillars 71 and upper and lower beams 72. The upper and lower beams 72 interconnect upper and lower ends of the pillars 71 through a pair of upper connectors and a pair of lower connectors 73. A pair of first joints 91 are respectively fixed to an aligned pair of the lower connectors 73, that are aligned in the folding direction, on each adjacent pair of the supporting frames 7. A pair of second joints 92 are mounted slidably and respectively on the lower beams 72 of each adjacent pair of the supporting frames 7. The crossing rods 81 of each of the foldable units 8 cross each other, are pivoted respectively to the first joints 91 on the adjacent pair of the supporting frames 7, and are further pivoted respectively to the second joints 92 on the adjacent pair of the supporting frames 7. The first linking rods 82 of each of the foldable units 8 are pivoted to each other through a respective one of the lower joints 86, and are further pivoted to the upper connectors on the adjacent pair of the supporting frames 7. The second linking rods 83 of each of the foldable units 8 are pivoted to each other through a respective one of the upper joints 85, are further pivoted to the lower connectors 73 on the adjacent pair of the supporting frames 7, and cross respectively the first linking rods 82. The middle beam 84 interconnects the lower joints 86. In use, the conventional foldable frame assembly is extended to a fully-extended position so as to support a mattress 4 thereon.
The conventional foldable frame assembly is disadvantageous in that each of the foldable units 8 requires too many parts, i.e., the crossing rods 81, the first and second linking rods 82, 83, the upper and lower joints 85, 86, and the middle beam 84, for providing sufficient supporting strength and stability for the foldable frame assembly, which results in an increase in assembly time and manufacturing costs.